Aphids (Hemiptera: Aphididae) on Plum and Cherry Plum in Bulgaria

The species complex and infestations of aphids on plum (Prunus persica) and cherry plum (Prunus cerasifera) in Bulgaria were investigated during the period 2013–2018. Nine species from the family Aphididae were found: Brachycaudus helichrysi Kaltenbach (leaf-curling plum aphid), Hyalopterus pruni Geoffroy (mealy plum aphid), Phorodon humuli Schrank (hop aphid), Brachycaudus prunicola Kaltenbach (brown plum aphid), Brachycaudus cardui Linnaeus (thistle aphid), Brachycaudus persicae Passerini (black peach aphid), Rhopalosiphum nymphaeae Linnaeus (waterlily aphid), Aphis spiraecola Patch (spiraea aphid) and Pterochloroides persicae Cholodkovsky (peach trunk aphid). The dominant species on plum are Hyalopterus pruni and Brachycaudus helichrysi. The first species is more widespread and of significantly higher density. The dominant species on cherry plum are Phorodon humuli and B. helichrysi. The species Brachycaudus prunicola is widespread both on plum and cherry plum in Bulgaria. It was found only on twigs, and therefore cannot be considered as a dangerous pest on fruit-bearing plum trees. The other species, some of them described as dangerous pests on plum, are today fairly rare and occur in low density, thus posing no danger to orchards.

Within-field distribution of the damson-hop aphid Phorodon humuli (Schrank) (Hemiptera: Aphididae) and natural enemies on hops in Spain

A field trial was performed in a hop yard throughout 2002, 2003 and 2004 in order to determine the within-field distribution of Phorodon humuli (Schrank) (Hemiptera: Aphididae) and its natural enemies. The distribution of P. humuli was directly affected by the position of the hop plants in the garden, with significantly higher concentrations of aphids (p=0.0122 in 2002 and p=0.0006 in 2003) observed along the edge. However, in 2004 the plants located on the marginal plots had similar populations to those on the more inner plots. This can be explained by a higher wind speed which made it more difficult to land on edge plants first. The hop aphid’s main natural enemy was Coccinella septempunctata (Coleoptera: Coccinellidae), whose population was greatest where the aphids were most abundant with a significantly greater number of eggs (p=0.0230) and adults (p=0.0245) in 2003. Lacewing eggs were also frequently observed, with a significantly higher population (p=0.0221 in 2003 and p=0.0046 in 2004) where the aphid numbers were high. The number of winged aphids was greatest towards the margins of the garden in 2003. It is argued that the spatial distribution of the hop aphid and its natural enemies could be used to plan a sampling program and to estimate the population densities of these insects for use in integrated pest management programs.